UFC light heavyweight champion Jon Jones (l.) with his brothers Chandler Jones of the Patriots (c.) and Arthur Jones of the Ravens.Tracy Lee/Combatlifestyle.com

Arthur Jones III wasn’t even a teenager when his older sister, Carmen, was diagnosed with brain cancer. Caring for her became a team effort, from parents Arthur Jr. and Camille to younger brothers Jon and Chandler.

“It kind of grew us up a lot earlier than were ready to grow up,” Arthur III said. “We knew how to put a feeding tube down someone’s throat. We learned how to care for someone who was very sick.”

Carmen died before her 18th birthday, never getting to see how incredibly successful her brothers would end up being.

This weekend is the culmination for the family from Endicott, N.Y.

Saturday night, Jon will defend his UFC light heavyweight title against Vitor Belfort at UFC 152 in Toronto. Win or lose, he then will hop on a plane to Baltimore to see the Ravens play host to the Patriots in a marquee NFL game Sunday night. Arthur III starts at defensive end for the Ravens, and Chandler is a rookie playing the same position for the Patriots.

“We’re definitely all very grateful to be where we’re at as a family,” Jon said.

Jon said it was “very hard” seeing his older sister suffer before she succumbed to cancer, but the Joneses are devout Christians, and there was acceptance when it was all over.

“We just knew she was in a better place,” Jon said. “We were all comfortable with the situation.”

Arthur III said the three brothers are “all each other’s best friends.” Jon said he’s “very excited” to see his brothers on opposite teams for the first time tomorrow.

It might be a little more difficult for Arthur III and Chandler to watch Jon compete. The two plan on going to dinner with Arthur Jr. and Camille this weekend in Baltimore, but Arthur III has curfew and can’t go out to watch Jon’s fight. He plans on trying to watch online in his hotel room.

“I get more nervous for [Jon’s] fights than my own football games,” Chandler said. “I’m sitting out there in the front row in the family seats. It’s a lot of tension leading up to the fight. He’s usually the main event, so I’m sitting there and my stomach is boiling waiting for him to come up in the Octagon.”

Chandler, a 22-year-old first-round pick from Syracuse, has 10 tackles and a sack in his first two games. Arthur III, 26, was a fifth-round selection in 2010 after starring for the Orange. Jon, 25, might be the most famous of the three. He became the youngest champion in UFC history at 23 in March 2011 when he beat Mauricio Rua, and is on track to become an all-time great in MMA.

As much as the three brothers talk, sports isn’t a big topic. They discuss hobbies, spirituality and life. A lot has changed since they were pre-teens helping to take care of their ill sister.

“We weren’t off playing video games,” Arthur III said. “We had to grow up a lost faster. It brought us a lot closer.”